Determination of antioxidant capacity by FRAP assay

FRAP assay to determine the antioxidant capacity of extracts was performed according to the method by Benzi and Strain,17 with minor modifications. FRAP solution was prepared in acetate buffer (pH 3.6). Various concentrations of each extract were prepared. The extract (2 mL) was added to 2 mL of FRAP (50 μg/mL). After incubation for 30 min, the absorbance was read at 593 nm. Ascorbic acid was used as the standard, FRAP (50 μg/mL) as the control, and acetate buffer as the blank. The antioxidant capacity was presented as EC₅₀ of FRAP capacity by determining the 50% exhibitory concentration using the calibration curve.